<s>
Display	B-Application
lag	I-Application
is	O
a	O
phenomenon	O
associated	O
with	O
most	O
types	O
of	O
liquid	B-Device
crystal	I-Device
displays	I-Device
(	O
LCDs	B-Device
)	O
like	O
smartphones	O
and	O
computers	O
and	O
nearly	O
all	O
types	O
of	O
high-definition	B-Device
televisions	I-Device
(	O
HDTVs	B-Device
)	O
.	O
</s>
<s>
It	O
refers	O
to	O
latency	O
,	O
or	O
lag	B-Application
between	O
when	O
the	O
signal	O
is	O
sent	O
to	O
the	O
display	O
and	O
when	O
the	O
display	O
starts	O
to	O
show	O
that	O
signal	O
.	O
</s>
<s>
This	O
lag	B-Application
time	O
has	O
been	O
measured	O
as	O
high	O
as	O
or	O
the	O
equivalent	O
of	O
3-4	O
frames	O
on	O
a	O
60	O
Hz	O
display	O
.	O
</s>
<s>
Display	B-Application
lag	I-Application
is	O
not	O
to	O
be	O
confused	O
with	O
pixel	O
response	O
time	O
,	O
which	O
is	O
the	O
amount	O
of	O
time	O
it	O
takes	O
for	O
a	O
pixel	O
to	O
change	O
from	O
one	O
brightness	O
value	O
to	O
another	O
.	O
</s>
<s>
Currently	O
the	O
majority	O
of	O
manufacturers	O
quote	O
the	O
pixel	O
response	O
time	O
,	O
but	O
neglect	O
to	O
report	O
display	B-Application
lag	I-Application
.	O
</s>
<s>
For	O
older	O
analog	O
cathode	B-Device
ray	I-Device
tube	I-Device
(	O
CRT	B-Device
)	O
technology	O
,	O
display	B-Application
lag	I-Application
is	O
nearly	O
zero	O
,	O
due	O
to	O
the	O
nature	O
of	O
the	O
technology	O
,	O
which	O
does	O
not	O
have	O
the	O
ability	O
to	O
store	O
image	O
data	O
before	O
display	O
.	O
</s>
<s>
The	O
picture	O
signal	O
is	O
minimally	O
processed	O
internally	O
,	O
simply	O
for	O
demodulation	B-Device
from	O
a	O
radio-frequency	O
(	O
RF	O
)	O
carrier	O
wave	O
(	O
for	O
televisions	O
)	O
,	O
and	O
then	O
splitting	O
into	O
separate	O
signals	O
for	O
the	O
red	O
,	O
green	O
,	O
and	O
blue	O
electron	O
guns	O
,	O
and	O
for	O
the	O
timing	O
of	O
the	O
vertical	O
and	O
horizontal	O
sync	O
.	O
</s>
<s>
For	O
either	O
over-the-air	O
or	O
cable	O
TV	O
,	O
the	O
same	O
analog	O
demodulation	B-Device
techniques	O
are	O
used	O
,	O
but	O
after	O
that	O
,	O
then	O
the	O
signal	O
is	O
converted	O
to	O
digital	O
data	O
,	O
which	O
must	O
be	O
decompressed	O
using	O
the	O
MPEG	O
codec	O
,	O
and	O
rendered	O
into	O
an	O
image	O
bitmap	O
stored	O
in	O
a	O
frame	B-Algorithm
buffer	I-Algorithm
.	O
</s>
<s>
For	O
progressive	B-Device
scan	I-Device
display	O
modes	O
,	O
the	O
signal	O
processing	O
stops	O
here	O
,	O
and	O
the	O
frame	B-Algorithm
buffer	I-Algorithm
is	O
immediately	O
written	O
to	O
the	O
display	O
device	O
.	O
</s>
<s>
This	O
is	O
done	O
by	O
storing	O
several	O
interlaced	O
frames	O
and	O
then	O
applying	O
algorithms	O
to	O
determine	O
areas	O
of	O
motion	O
and	O
stillness	O
,	O
and	O
to	O
either	O
merge	O
interlaced	O
frames	O
for	O
smoothing	O
or	O
extrapolate	O
where	O
pixels	O
are	O
in	O
motion	O
,	O
the	O
resulting	O
calculated	O
frame	B-Algorithm
buffer	I-Algorithm
is	O
then	O
written	O
to	O
the	O
display	O
device	O
.	O
</s>
<s>
De-interlacing	O
imposes	O
a	O
delay	O
that	O
can	O
be	O
no	O
shorter	O
than	O
the	O
number	O
of	O
frames	O
being	O
stored	O
for	O
reference	O
,	O
plus	O
an	O
additional	O
variable	O
period	O
for	O
calculating	O
the	O
resulting	O
extrapolated	O
frame	B-Algorithm
buffer	I-Algorithm
;	O
delays	O
of	O
16-32ms	O
are	O
common	O
.	O
</s>
<s>
While	O
the	O
pixel	O
response	O
time	O
of	O
the	O
display	O
is	O
usually	O
listed	O
in	O
the	O
monitor	O
's	O
specifications	O
,	O
no	O
manufacturers	O
advertise	O
the	O
display	B-Application
lag	I-Application
of	O
their	O
displays	O
,	O
likely	O
because	O
the	O
trend	O
has	O
been	O
to	O
increase	O
display	B-Application
lag	I-Application
as	O
manufacturers	O
find	O
more	O
ways	O
to	O
process	O
input	O
at	O
the	O
display	O
level	O
before	O
it	O
is	O
shown	O
.	O
</s>
<s>
Possible	O
culprits	O
are	O
the	O
processing	O
overhead	O
of	O
HDCP	B-Protocol
,	O
Digital	O
Rights	O
Management	O
(	O
DRM	O
)	O
,	O
and	O
also	O
DSP	B-General_Concept
techniques	O
employed	O
to	O
reduce	O
the	O
effects	O
of	O
ghosting	O
–	O
and	O
the	O
cause	O
may	O
vary	O
depending	O
on	O
the	O
model	O
of	O
display	O
.	O
</s>
<s>
LCD	B-Device
,	O
plasma	O
,	O
and	O
DLP	O
displays	O
,	O
unlike	O
CRTs	O
,	O
have	O
a	O
native	B-General_Concept
resolution	I-General_Concept
.	O
</s>
<s>
That	O
is	O
,	O
they	O
have	O
a	O
fixed	O
grid	O
of	O
pixels	O
on	O
the	O
screen	O
that	O
show	O
the	O
image	O
sharpest	O
when	O
running	O
at	O
the	O
native	B-General_Concept
resolution	I-General_Concept
(	O
so	O
nothing	O
has	O
to	O
be	O
scaled	O
full-size	O
which	O
blurs	O
the	O
image	O
)	O
.	O
</s>
<s>
As	O
an	O
example	O
,	O
a	O
display	O
that	O
has	O
a	O
native	B-General_Concept
resolution	I-General_Concept
of	O
1600x1200	O
being	O
provided	O
a	O
signal	O
of	O
640x480	O
must	O
scale	O
width	O
and	O
height	O
by	O
2.5x	O
to	O
display	O
the	O
image	O
provided	O
by	O
the	O
computer	O
on	O
the	O
native	O
pixels	O
.	O
</s>
<s>
Interlaced	O
video	O
signals	O
such	O
as	O
480i	O
and	O
1080i	O
require	O
a	O
deinterlacing	O
step	O
that	O
adds	O
lag	B-Application
.	O
</s>
<s>
Anecdotally	O
,	O
display	B-Application
lag	I-Application
is	O
significantly	O
less	O
when	O
displays	O
operate	O
in	O
native	B-General_Concept
resolutions	I-General_Concept
for	O
a	O
given	O
LCD	B-Device
screen	I-Device
and	O
in	O
a	O
progressive	B-Device
scanning	I-Device
mode	O
.	O
</s>
<s>
External	O
devices	O
have	O
also	O
been	O
shown	O
to	O
reduce	O
overall	O
latency	O
by	O
providing	O
faster	O
image-space	O
resizing	O
algorithms	O
than	O
those	O
present	O
in	O
the	O
LCD	B-Device
screen	I-Device
.	O
</s>
<s>
Many	O
LCDs	B-Device
also	O
use	O
a	O
technology	O
called	O
"	O
overdrive	O
"	O
which	O
buffers	O
several	O
frames	O
ahead	O
and	O
processes	O
the	O
image	O
to	O
reduce	O
blurring	O
and	O
streaks	O
left	O
by	O
ghosting	O
.	O
</s>
<s>
Display	B-Application
lag	I-Application
can	O
be	O
measured	O
using	O
a	O
test	O
device	O
such	O
as	O
the	O
Video	O
Signal	O
Input	B-Application
Lag	I-Application
Tester	O
.	O
</s>
<s>
Despite	O
its	O
name	O
,	O
the	O
device	O
cannot	O
independently	O
measure	O
input	B-Application
lag	I-Application
.	O
</s>
<s>
It	O
can	O
only	O
measure	O
input	B-Application
lag	I-Application
and	O
response	O
time	O
together	O
.	O
</s>
<s>
Lacking	O
a	O
measurement	O
device	O
,	O
measurement	O
can	O
be	O
performed	O
using	O
a	O
test	O
display	O
(	O
the	O
display	O
being	O
measured	O
)	O
,	O
a	O
control	O
display	O
(	O
usually	O
a	O
CRT	B-Device
)	O
that	O
would	O
ideally	O
have	O
negligible	O
display	B-Application
lag	I-Application
,	O
a	O
computer	O
capable	O
of	O
mirroring	O
an	O
output	O
to	O
the	O
two	O
displays	O
,	O
stopwatch	O
software	O
,	O
and	O
a	O
high-speed	O
camera	O
pointed	O
at	O
the	O
two	O
displays	O
running	O
the	O
stopwatch	O
program	O
.	O
</s>
<s>
The	O
lag	B-Application
time	O
is	O
measured	O
by	O
taking	O
a	O
photograph	O
of	O
the	O
displays	O
running	O
the	O
stopwatch	O
software	O
,	O
then	O
subtracting	O
the	O
two	O
times	O
on	O
the	O
displays	O
in	O
the	O
photograph	O
.	O
</s>
<s>
This	O
method	O
only	O
measures	O
the	O
difference	O
in	O
display	B-Application
lag	I-Application
between	O
two	O
displays	O
and	O
cannot	O
determine	O
the	O
absolute	O
display	B-Application
lag	I-Application
of	O
a	O
single	O
display	O
.	O
</s>
<s>
CRTs	O
are	O
preferable	O
to	O
use	O
as	O
a	O
control	O
display	O
because	O
their	O
display	B-Application
lag	I-Application
is	O
typically	O
negligible	O
.	O
</s>
<s>
As	O
seen	O
on	O
different	O
monitor	O
reviews	O
the	O
so	O
determined	O
values	O
for	O
the	O
display	B-Application
lag	I-Application
for	O
the	O
very	O
same	O
monitor	O
model	O
differ	O
by	O
margins	O
up	O
to	O
or	O
even	O
more	O
.	O
</s>
<s>
Several	O
approaches	O
to	O
measure	O
display	B-Application
lag	I-Application
have	O
been	O
restarted	O
in	O
slightly	O
changed	O
ways	O
but	O
still	O
reintroduced	O
old	O
problems	O
,	O
that	O
have	O
already	O
been	O
solved	O
by	O
the	O
former	O
mentioned	O
SMTT	O
.	O
</s>
<s>
One	O
such	O
method	O
involves	O
connecting	O
a	O
laptop	O
to	O
an	O
HDTV	B-Device
through	O
a	O
composite	O
connection	O
and	O
run	O
a	O
timecode	O
that	O
shows	O
on	O
the	O
laptop	O
's	O
screen	O
and	O
the	O
HDTV	B-Device
simultaneously	O
and	O
recording	O
both	O
screens	O
with	O
a	O
separate	O
video	O
recorder	O
.	O
</s>
<s>
When	O
the	O
video	O
of	O
both	O
screens	O
is	O
paused	O
,	O
the	O
difference	O
in	O
time	O
shown	O
on	O
both	O
displays	O
have	O
been	O
interpreted	O
as	O
an	O
estimation	O
for	O
the	O
display	B-Application
lag	I-Application
.	O
</s>
<s>
Nevertheless	O
,	O
this	O
is	O
almost	O
identical	O
to	O
the	O
use	O
of	O
casual	O
stopwatches	O
on	O
two	O
monitors	O
using	O
a	O
"	O
clone	O
view	O
"	O
monitor	O
setup	O
as	O
it	O
does	O
not	O
care	O
about	O
the	O
missing	O
synchronisation	O
between	O
the	O
composite	O
video	O
signal	O
and	O
the	O
display	O
of	O
the	O
laptop	O
's	O
screen	O
or	O
the	O
display	B-Application
lag	I-Application
of	O
that	O
screen	O
or	O
the	O
detail	O
that	O
the	O
vertical	O
screen	O
refresh	O
of	O
the	O
two	O
monitors	O
is	O
still	O
asynchronous	O
and	O
not	O
linked	O
to	O
each	O
other	O
.	O
</s>
<s>
Therefore	O
,	O
it	O
is	O
impossible	O
to	O
use	O
a	O
single	O
stop	O
watch	O
for	O
display	B-Application
lag	I-Application
measurements	O
,	O
nevertheless	O
if	O
it	O
is	O
created	O
by	O
a	O
timecode	O
or	O
a	O
simple	O
stopwatch	O
application	O
,	O
as	O
it	O
will	O
always	O
cause	O
an	O
error	O
of	O
up	O
to	O
or	O
even	O
more	O
.	O
</s>
<s>
Display	B-Application
lag	I-Application
contributes	O
to	O
the	O
overall	O
latency	O
in	O
the	O
interface	O
chain	O
of	O
the	O
user	O
's	O
inputs	O
(	O
mouse	O
,	O
keyboard	O
,	O
etc	O
.	O
)	O
</s>
<s>
Depending	O
on	O
the	O
monitor	O
,	O
display	B-Application
lag	I-Application
times	O
between	O
have	O
been	O
measured	O
.	O
</s>
<s>
Display	B-Application
lag	I-Application
is	O
most	O
noticeable	O
in	O
games	O
(	O
especially	O
older	O
video-game	O
consoles	O
)	O
,	O
with	O
different	O
games	O
affecting	O
the	O
perception	O
of	O
delay	O
.	O
</s>
<s>
For	O
instance	O
,	O
in	O
World	B-Protocol
of	I-Protocol
Warcraft	I-Protocol
's	O
PvE	O
,	O
a	O
slight	O
input	O
delay	O
is	O
not	O
as	O
critical	O
compared	O
to	O
PvP	O
,	O
or	O
to	O
other	O
games	O
favoring	O
quick	O
reflexes	O
like	O
Counter-Strike	B-Application
.	O
</s>
<s>
Rhythm-based	O
games	O
,	O
such	O
as	O
Guitar	B-Application
Hero	I-Application
,	O
also	O
require	O
exact	O
timing	O
;	O
display	B-Application
lag	I-Application
will	O
create	O
a	O
noticeable	O
offset	O
between	O
the	O
music	O
and	O
the	O
on-screen	O
prompts	O
.	O
</s>
<s>
Notably	O
,	O
many	O
games	O
of	O
this	O
type	O
include	O
an	O
option	O
that	O
attempts	O
to	O
calibrate	O
for	O
display	B-Application
lag	I-Application
.	O
</s>
<s>
Arguably	O
,	O
fighting	O
games	O
such	O
as	O
Street	B-Application
Fighter	I-Application
,	O
Super	B-Application
Smash	I-Application
Brothers	I-Application
Melee	I-Application
and	O
Tekken	B-Application
are	O
the	O
most-affected	O
,	O
since	O
they	O
may	O
require	O
move	O
inputs	O
within	O
extremely	O
tight	O
event	O
windows	O
that	O
sometimes	O
only	O
last	O
1	O
frame	O
or	O
16.67	O
ms	O
on	O
the	O
screen	O
.	O
</s>
<s>
By	O
assuming	O
a	O
Gaussian	O
human	O
response	O
time	O
to	O
a	O
particular	O
in-game	O
event	O
,	O
it	O
becomes	O
possible	O
to	O
discuss	O
the	O
effect	O
of	O
lag	B-Application
in	O
terms	O
of	O
probabilities	O
.	O
</s>
<s>
Given	O
a	O
lag-less	O
display	O
,	O
a	O
human	O
has	O
a	O
certain	O
probability	O
to	O
land	O
his/her	O
input	O
within	O
a	O
window	O
of	O
frames	O
.	O
</s>
<s>
Because	O
of	O
this	O
,	O
any	O
amount	O
of	O
lag	B-Application
will	O
affect	O
a	O
human	O
's	O
ability	O
to	O
hit	O
a	O
particular	O
timing	O
window	O
.	O
</s>
<s>
The	O
severity	O
of	O
this	O
impact	O
is	O
a	O
function	O
of	O
the	O
position	O
and	O
variance	O
of	O
a	O
human	O
's	O
response	O
to	O
a	O
visual	O
cue	O
,	O
the	O
amount	O
of	O
lag	B-Application
introduced	O
,	O
and	O
the	O
size	O
of	O
the	O
timing	O
window	O
.	O
</s>
<s>
By	O
introducing	O
one	O
frame	O
of	O
lag	B-Application
,	O
the	O
human	O
's	O
ability	O
to	O
hit	O
the	O
30	O
frame	O
window	O
would	O
likely	O
remain	O
in	O
the	O
99.99	O
%	O
range	O
(	O
assuming	O
the	O
human	O
is	O
responding	O
somewhere	O
near	O
the	O
middle	O
of	O
the	O
window	O
)	O
.	O
</s>
<s>
Given	O
a	O
smaller	O
window	O
of	O
say	O
2	O
frames	O
,	O
however	O
,	O
the	O
effect	O
of	O
lag	B-Application
becomes	O
much	O
more	O
significant	O
.	O
</s>
<s>
Assuming	O
the	O
human	O
's	O
response	O
is	O
centered	O
on	O
the	O
2	O
frame	O
window	O
and	O
the	O
super-human	O
has	O
a	O
99.99	O
%	O
chance	O
to	O
hit	O
the	O
window	O
,	O
introducing	O
a	O
full	O
frame	O
of	O
lag	B-Application
causes	O
the	O
success	O
rate	O
to	O
drop	O
all	O
the	O
way	O
to	O
about	O
50%	O
.	O
</s>
<s>
If	O
the	O
game	O
's	O
controller	O
produces	O
additional	O
feedback	O
(	O
rumble	O
,	O
the	O
Wii	B-Device
Remote	I-Device
's	O
speaker	O
,	O
etc	O
.	O
</s>
<s>
)	O
,	O
then	O
the	O
display	B-Application
lag	I-Application
will	O
cause	O
this	O
feedback	O
to	O
not	O
accurately	O
match	O
up	O
with	O
the	O
visuals	O
on-screen	O
,	O
possibly	O
causing	O
extra	O
disorientation	O
(	O
e.g.	O
</s>
<s>
If	O
a	O
home	O
theater	O
receiver	O
with	O
external	O
speakers	O
is	O
used	O
,	O
then	O
the	O
display	B-Application
lag	I-Application
causes	O
the	O
audio	O
to	O
be	O
heard	O
earlier	O
than	O
the	O
picture	O
is	O
seen	O
.	O
</s>
<s>
Many	O
televisions	O
,	O
scalers	O
and	O
other	O
consumer-display	O
devices	O
now	O
offer	O
what	O
is	O
often	O
called	O
a	O
"	O
game	O
mode	O
"	O
in	O
which	O
the	O
extensive	O
preprocessing	O
responsible	O
for	O
additional	O
lag	B-Application
is	O
specifically	O
sacrificed	O
to	O
decrease	O
,	O
but	O
not	O
eliminate	O
,	O
latency	O
.	O
</s>
<s>
Similar	O
options	O
have	O
long	O
been	O
available	O
on	O
home	O
audio	O
hardware	O
and	O
modems	B-Application
for	O
the	O
same	O
reason	O
.	O
</s>
<s>
Connection	O
through	O
VGA	O
cable	O
or	O
component	O
should	O
eliminate	O
perceivable	O
input	B-Application
lag	I-Application
on	O
many	O
TVs	O
even	O
if	O
they	O
already	O
have	O
a	O
game	O
mode	O
.	O
</s>
<s>
A	O
television	O
may	O
have	O
a	O
picture	O
mode	O
that	O
reduces	O
display	B-Application
lag	I-Application
for	O
computers	O
.	O
</s>
<s>
Some	O
Samsung	O
and	O
LG	O
televisions	O
automatically	O
reduce	O
lag	B-Application
for	O
a	O
specific	O
input	O
port	O
if	O
the	O
user	O
renames	O
the	O
port	O
to	O
"	O
PC	O
"	O
.	O
</s>
<s>
LCD	B-Device
screens	I-Device
with	O
a	O
high	O
response-time	O
value	O
often	O
do	O
not	O
give	O
satisfactory	O
experience	O
when	O
viewing	O
fast-moving	O
images	O
(	O
they	O
often	O
leave	O
streaks	O
or	O
blur	O
;	O
called	O
ghosting	O
)	O
.	O
</s>
<s>
But	O
an	O
LCD	B-Device
screen	I-Device
with	O
both	O
high	O
response	O
time	O
and	O
significant	O
display	B-Application
lag	I-Application
is	O
unsuitable	O
for	O
playing	O
fast-paced	O
computer	O
games	O
or	O
performing	O
fast	O
high-accuracy	O
operations	O
on	O
the	O
screen	O
,	O
due	O
to	O
the	O
mouse	O
cursor	O
lagging	O
behind	O
.	O
</s>
